1. Field of the Invention
This invention relates to container closures which provide evidence of tampering. More particularly, it relates to such closures having a tamper indicating band secured to a radial flange on a container neck by hook like locking tabs and connected to a cap by extendable bridges which fracture upon removal of the cap. The invention also relates to such caps which can be molded with straight draw molding techniques without the need for slides or inserts.
2. Background Information
It is common practice today to provide container closures with devices which indicate whether the closure has been opened or tampered with. A common type of such closures utilizes an annular ring or tamper indicting band which is connected to a conventional cap, such as a screw cap, by frangible connecting ribs or bridges. The tamper indicating band is secured to the container, such that when the cap is removed, the connecting ribs or bridges fracture to provide a positive, visual and mechanical indication of cap removal or tampering.
A common arrangement for securing the tamper indicating band to the container is to provide a radially inwardly directed flange or fingers which engage a radially outwardly projecting flange on the container neck, commonly known as a transfer bead because the container is often transported by devices which lift the container by this flange. One drawback of such tamper evident closures is that they create undercuts. Closures with such undercuts cannot be integrally molded using a straight draw mold. That is, a mold in which all of the features of the molded product are embodied in two halves of the mold which can merely be pulled apart. In order to incorporate the undercuts, lateral slides are typically used in the mold, which complicates both the mold and the molding process.
In some closures, the tamper indicating band is secured to the transfer bead on the container by hook-like locking tabs which project axially, as well as radially inward, from the tamper indicating band. Examples of such closures are shown in U.S. Pat. Nos. 4,394,918; 4,550,844; and 4,506,795. The closures of these patents require lateral slides to mold the hook-like locking tabs, and/or, post molding steps to form the hook in the tab. These closures also require lateral slides or post molding steps to form the frangible section along which the tamper indicating band separates from the cap as the cap is removed from the container or tampered with. Such lateral mold slides and post molding steps add cost and time to the production of tamper evident closures.
There is a need, therefore, for an improved closure with a tamper indicating band for engaging a transfer bead on a container which can be integrally molded in a straight draw mold without slides or inserts.
There is a further need for such a closure which has the improved gripping capability provided by hook-like locking tabs which engage the transfer bead on the container.
There is also a need for such a closure which does not require post molding operations.
There is an additional need for such a closure having flexible frangible bridges connecting the tamper indicating band to the remainder of the closure so that the closure may be used with containers having variable spacing between the threads securing the cap to the container and the transfer bead, and so that tolerances in the dimensions on the closure and container can be loose.
There is a related need for such a closure having arrangements for applying the force required to push the locking tabs on the tamper indicating band past the transfer bead without overstressing the frangible bridges connecting the tamper indicating band to the cap.